Molding method of air bag cover

Abstract

A molding method is used to produce a module cover for an air bag device which has undercut portions in mounting edge portions thereof. A lower mold disposed inside the module cover to be produced is of the split type so that is includes a central mold disposed at the center and a plurality of lateral molds for molding of the undercut portions. The mating face of the central mold with each lateral mold is oblique so that its bottom is closer to the edge of the module cover than its top. Thus, the module cover produced can be detached from the lower mold by moving the lateral molds mutually inward.

What is claimed is: 
     
       1. A method of molding a module cover for an air bag device of first and second synthetic resin materials, the module cover having a main cover portion, edge portions, and at least one pair of undercut portions formed at the edge portions of the main cover portion, comprising, preparing first and second upper molds for forming an outside of the main cover portion, and a lower mold for forming an inside of the main cover portion and the undercut portions, the first upper mold being smaller than the second upper mold, the lower mold including a central mold for molding a central section of the inside of the main cover portion, at least one pair of lateral molds for molding side sections of the inside of the main cover portion and insides of the edge portions and the undercut portions, the pair of lateral molds being arranged symmetrical to the central mold, and a frame mold for molding outsides of the edge portions and the undercut portions, the central mold and the frame mold being connected together as one unit, the central mold and the lateral molds having oblique mating faces so that the lateral molds are slidable laterally to be located above the central mold away from the edge portions of the module cover,   disposing the first upper mold over the lower mold to define a first cavity therebetween,   injecting the first resin material into the first cavity and hardening the first resin material to form a core layer comprising the main cover portion, the edge portions and the undercut portions of the module cover,   removing the first upper mold and placing the second upper mold over the main cover portion of the core layer in engagement with the lower mold, to form a second cavity between the core layer and the second upper mold about the main cover portion of the core layer,   injecting the second resin material into the second cavity and hardening the second resin material to form a skin layer over the main cover portion of the core layer,   removing the second upper mold from the skin layer,   separating the frame mold and the central mold as one unit from the core layer while moving inside the core layer the lateral molds toward each other slidably along the oblique mating faces of the lateral molds and the central mold so that the lateral molds are located away from the edge portions of the core layer, and   removing the lateral molds from the core layer to form the module cover comprising the main cover portion, the edge portions, and the at least one pair of undercut portions formed at the edge portions, wherein the main cover portion includes the core layer of the first synthetic resin material and the skin layer of the second synthetic resin material.   
     
     
       2. A molding method according to claim 1, wherein the module cover is laterally elongated, the undercut portions being formed at laterally elongated portions of the module cover, the lateral molds being arranged to be movable relative to the laterally elongated portions of the module cover.